New horse tests positive for the equine herpesvirus at the Marion duPont Scott Equine Medical Center.

A sixth Virginia horse has tested positive for the equine herpesvirus (EHV-1) that shut down several farms and hospitals in Loudoun two weeks ago. The Virginia Department of Agriculture and Consumer Services announced March 2 that another horse at Virginia Tech's Marion duPont Scott Equine Medical Center at Morven Park in Leesburg had tested positive for the disease. The veterinarian hospital has been under quarantined since Feb. 20. All six of the horses that have tested positive for EHV-1 have showed signs of neurological disease.

"This new confirmation indicates that more horses on this particular farm may have been exposed, but we are hopeful that our quarantine has prevented exposure of other horses in the area," Dr. Richard Wilkes, a Virginia state veterinarian, said in a press release. "We will continue to monitor this farm, as well as others, until the threat of EHV-1 has passed."

The VDACS is "guardedly optomistic" that the virus has not spread to other horses in Virginia. The disease can have an incubation period from one to 10 days and horses can remain infectious for three to four weeks. Horses in both Faquier and Culpeper counties have tested negative for the virus.

EVH-1 IS ONE of several strains of the equine herpesvirus, a highly contagious disease that can cause respiratory signs, prenatal infection, abortion, inflammation of the brain. This strain of herpesvirus is not transmissible to humans, but can be transferred between horses through nasal fluids and bodily secretions. Symptoms of the virus include fever, coughing, nasal discharge, loss of balance and recumbency, or lying down. On Feb. 7, a horse that had been brought to the Marion duPont Scott Equine Medical Center for an unrelated emergency developed a fever and symptoms of the nervous disease, Dr. Nathanial A. White II, the Jean Ellen Shehan professor and director of the equine center, said. The horse was immediately isolated, the doctor said, and tested positive for EHV-1 Feb. 16.

The morning of Feb. 20 two more horses at the veterinary hospital began to show neurological symptoms, leading the Virginia Department of Agriculture and Consumer Services to order quarantine beginning that day.

White said that up to 70 percent of horses can carry the virus in their system without showing any symptoms and the disease is difficult to eliminate because of its dormant nature.

"Most of the treatment is symptomatic treatment, until the virus runs its course," White said. "But this [neurological] form is actually rare in horses. It can actually be fatal."